Americans are wringing their hands about the grave threat that a nuclear Iran would pose to the United States. But the numbers tell a different story.

As a contentious new round of high-stakes nuclear talks between Iran and world powers wraps up in Baghdad, it is important to think critically about how much of a threat Iran poses to the United States. According to former senator Rick Santorum, for example, a nuclear Iran would have “carte blanche to spread a reign of terror around not just the Middle East, but here in America … [and] across Western civilization.” Republican presidential candidate Mitt Romney has argued that “if the Iranians are permitted to get the bomb, the consequences will be as uncontrollable as they are horrendous.” Several leading U.S. senators penned an op-ed in March stating that “the prospect of a nuclear-armed Iran is a threat to the entire world, including particularly the U.S.”

It is not just politicians who hold these views. A recent CNN poll revealed that more than three-quarters of the American public sees Iran and North Korea as “serious” threats while only 44 percent feels the same way about Russia. Indeed, fear of the Iranian threat in the United States is more widespread today than fear of the Soviet threat was in 1985, even though at that time the Soviet Union possessed the largest nuclear arsenal in the world and today Iran doesn’t have a single nuclear weapon.

Which raises an obvious question: Does the dominant perception of the Iranian threat actually square with reality? To answer that question, we designed the Nuclear Annihilation Threat (NAT) Index — a way of systematically and empirically assessing the existential threat that nuclear-weapon states (NWSs), and potential nuclear-weapon states, pose to one another. What we found is striking: Although Israel is right to see Iran as an existential danger, the United States has blown the Iranian threat to itself all out of proportion — and Iran is unlikely to find existential security in a nuclear weapon. In addition, both Israel and the United States should be focusing much more aggressively on the threat posed by Pakistan.

Unlike any other weapon, nuclear weapons can jeopardize a nation’s very existence. We use the term “existential threat” to denote the capability of one state to completely annihilate another. In concrete terms, a nuclear attack on one U.S. city would be catastrophic, but it would not destroy the United States. A similar nuclear attack on Tel Aviv, on the other hand, would potentially kill 42 percent of the Israeli population and most likely spell the end of the Jewish state. By focusing exclusively on existential dangers, we seek to understand how nuclear weapons affect the core survival motivations that drive states’ behavior. While this may be a narrow perspective, we think that isolating this unique characteristic of nuclear weapons yields important insights.

Our NAT Index is a relational metric that draws on four factors in determining the existential threats that nuclear-armed countries pose to one another: 1) the potential damage acountry’s nuclear arsenal could cause to a target’s population; 2) the ability of a country to strike a target with ballistic missiles; 3) the presence of a strategic rivalry between the two countries; and 4) the risk ofstate failure in the country that is hypothetically attacking a target. The NAT Index can also be used to identify which nuclear-armed countries pose the greatest existential threats overalland which are the most vulnerable.

Pakistan’s nuclear arsenal, for example, is capable of inflicting higher levels of proportional damage to a country the size of Israel than a country the size of China because of geographic and demographic differences. Countries that are rivals of North Korea and are within range of its ballistic missiles face a greater existential threat from Pyongyang than those that are not.We factor in the risk of state failure because an unstable country’s leaders and governmental policies can change on a dime and destabilized regimes can lose command and control of their nuclear weapons, exposing the arms to theft or unauthorized use.

While our index accounts for the heightened existential risks created by rivalries, we do not assume that nuclear-armed allies pose no risks to one another. From a realist perspective, the military power of other states can never be safely ignored — especially with respect to weapons that possess such uniquely destructive power. Beyond realism’s admonishment that today’s allies could become tomorrow’s rivals, the risks of nuclear weapons accidents and misuse exist between both rivals and allies. While it may appear odd to consider Britain as a potential nuclear threat to the United States, remember that Pakistan is also a U.S. ally. In accounting for the threats that even allies’ nuclear weapons pose, our analysis reflects the view that all nuclear weapons — no matter who possesses them — present a grave international security threat.

We coded our NAT Index using the most recent publicly available data. To account for the potential nuclear destruction a country could inflict on a target, we compared the number of nuclear weapons the state possesses to the number of population centers over one million people in the target country. Assuming that it would take four nuclear weapons to ensure destruction of a population center, we noted whether a state could destroy less than 25 percent of a target’s urban centers, 25 to 75 percent of them, or more than 75 percent of them. We classified a country as being able to strike a target with its ballistic missiles if it possesses known ballistic missile capabilities that would allow it to strike any part of a target’s territory. States engaged in strategic rivalries were identified via a highly regarded international relations data set on the subject. Lastly, we coded the country as constituting a state failure threat if it was identified as being at critical risk in Foreign Policy’s 2011 Failed States Index. Like any effort to systematically analyze nuclear threats, the results of our analysis are shaped by the assumptions we make and the data we use. We thus encourage readers to learn more about our methodology we use in the appendix we have provided.

Using the method of aggregation displayed below, our NAT Index produces a measure of the existential threat a state poses to a target state on a scale from .05 (minimal threat) to 9 (maximal threat).

The NAT Index suggests that American fears about the existential threats posed by Iran and North Korea being on par with those posed by Russia are misplaced. Our results in Table 1 indicate that China and Russia constitute the largest existential threats to the United States, while North Korea actually represents the smallest annihilation threat. Intuitively, this makes sense given the large size of the Chinese and Russian nuclear arsenals and their advanced delivery capabilities. In contrast, the small nuclear arsenal possessed by North Korea could only threaten a small number of U.S. cities (even if Pyongyang’s ballistic missiles actually worked) but does not jeopardize the United States’ existence. When we simulate Iran going nuclear by assuming that it acquires 10 nuclear weapons (roughly the size of North Korea’s arsenal) and that it will be able to deliver those weapons via ballistic missiles, we find that Iran represents a minimal existential threat to the United States.

Israeli fears of Iran going nuclear, on the other hand, are well-justified. In the current strategic environment, captured in Table 2, Pakistan represents the greatest existential threat to Israelbecause of its nuclear capability, domestic instability, and hostility to Israel (not to mention the greater hostility that violent jihadi groups in the country harbor toward the Jewish state). India and North Korea, meanwhile, constitute the smallest annihilation threats. When we include Iran in our rankings, however, it emerges as Israel’s greatest existential threat.

We can also look at the overall threat each NWS poses by averaging its annihilation threat scores vis-à-vis other nuclear-armed states.When we do this, we find that Pakistan — because of its high risk of state failure and its central location relative to other nuclear weapons states — poses the greatestannihilation threat to other members of the nuclear weapons club. North Korea, by contrast, poses the smallest annihilation threat to other nuclear weapons states. When we integrate Iran into the analysis in Table 3, it poses a similarly small annihilation threat to the other NWSs in aggregate despite the significant threat it poses to Israel. This may explain why countries such as Britain and France view the prospect of Iran going nuclear as more of a policy concern than a major threat.

Looking instead at the average vulnerabilities of NWSs, the consequences of Iran going nuclear are even more striking. The rankings in Table 4 indicate that, in the current strategic environment, Russia faces the greatest existential threat, while Britain and France face the lowest threats. Israel does not face a major existential threat under existing conditions.

Yet if Iran goes nuclear under our scenario, Israel will become one of the most vulnerable nuclear-armed states. Iran, for its part, will actually become the most existentially vulnerable NWS if it goes nuclear. This does not necessarily imply that acquiring nuclear weapons would negatively affect Iran’s national security, but it does suggest that Iran would be joining the nuclear weapons club as one of its weakest, most at-risk members.

So what do these findings tell us about the current strategic environment and the potential fallout from Iran obtaining nuclear weapons? First, they indicate that the primary existential threat to the United States emanates from China and Russia — not rogue states such as Iran and North Korea. This supports the notion that nuclear arms reduction agreements like New START offer the United States significant national security benefits.

Second, our findings suggest that more U.S. and international attention should be given to the existing nuclear threat posed by Pakistan than the still-hypothetical threat posed by Iran. Stabilizing Pakistan to prevent its collapse and using strategic trade controls to limit its access to ballistic missile and nuclear weapons technologies should be priorities in the international community.

Third, our results help explain the relative passivity of some NWSs about allowing Iran to march ever closer to obtaining nuclear weapons — and Israel’s horror at the proposition. That said, Iran would become the world’s most existentially vulnerable NWS if it went nuclear. Nuclear weapons would not enhance Iran’s security as much as some may think, and that should make its leaders think twice about acquiring a nuclear capability.

Our findings underline the challenges that a nuclear Iran poses for the United States. On the one hand, it is clear that Iran would not pose an existential threat to the United States any time soon, even if it obtained nuclear weapons. On the other hand, it is equally clear that a nuclear-armed Iran would pose a large existential threat to one of America’s closest allies in the Middle East. It could also fundamentally alter the relationships that Iran has with its non-nuclear neighbors and drive some of those countries toward proliferating. Similarly, North Korea poses a minimal existential threat to the United States but a serious threat to U.S. allies in Asia. North Korea, in fact, may represent even more of a policy conundrum for the United States because it is in more serious danger of state failure than Iran.

Today’s myopic focus on Iran, moreover, is distracting many (but clearly not all) from paying closer attention to the serious nuclear threat posed by Pakistan. In Foreign Policy’s Failed States Index, Pakistan is ranked 12th in terms of the risk of state failure and is the only nuclear-armed country labeled in “critical” condition. One recent Nuclear Threat Initiative study noted that the country faces “immense threats, both from insiders who may be corrupt or sympathetic to terrorists and from large-scale attacks by outsiders.” For the United States and its allies, a more sustained focus on Pakistan and its extant nuclear weapons is imperative even as the United States and Israel try to neutralize the Iranian threat while avoiding a war.

Authors: VICTOR ASAL is an associate professor in the political science department at the University at Albany – SUNY.

BRYAN EARLY is an assistant professor in the political science department and public administration & policy departmentat the University at Albany – SUNY.